Hydraulic fracturing is a primary tool for improving well productivity by placing or extending channels from the wellbore to the reservoir. This operation is essentially performed by hydraulically injecting a fracturing fluid into a wellbore penetrating a subterranean formation and forcing the fracturing fluid against the formation strata by pressure. The formation strata or rock is forced to crack, creating or enlarging one or more fractures. Proppant is placed in the fracture to prevent the fracture from closing and thus the fracture provides improved flow of the recoverable fluids, i.e. oil, gas or water.
The proppant is thus used to hold the walls of the fracture apart to create a conductive path to the wellbore after pumping has stopped. Placing the appropriate proppant at the appropriate concentration to form a suitable proppant pack is thus critical to the success of a hydraulic fracture treatment.
The geometry of the hydraulic fracture placed directly affects the efficiency of the process and the success of the operation. However, there are currently no direct methods of measuring the dimensions of a hydraulic fracture. The three methods currently used, pressure analysis, tiltmeter observational analysis, and microseismic monitoring of hydraulic fracture growth all require de-convolution of the acquired data for the fracture geometry to be inferred through the use of models—which is highly dependent on key assumptions—and often the results of these analyses verge on conjecture. All these methods use indirect measurements and are difficult to use except for post-job analysis rather than real-time evaluation and optimization of the hydraulic treatment. Moreover, these methods provide little information as to the actual shape of the propped fracture.
It is therefore an object of the present invention to provide a new approach to evaluating hydraulic fracture geometry.